Frigg

Frigg is a great dragon when you first get her. Chain lightning is great for taking out multiple targets at once, and the ability to use multi-touch whilst attacking means that towers are taken down seriously fast. Frigg is amazingly fast to heal after taking no damage, and is often strategically used in events like conquer to apply an extra boost once the base is defeated to earn more acres without the need for a potion to bring her back.